PROJECT SUMMARY - Sex-based differences in oral HPV infections and outcomes Many infectious diseases exhibit differential severity between the sexes yet the mechanisms driving such innate biases are incompletely understood. The prevalence of human papillomavirus (HPV) oral infections and HPV-associated oropharyngeal cancers are 3- to 5-fold more common in men than women. This correlates only partially (~18%) with behavioral risk factors which would indicate that males have higher HPV exposure. Other possible explanations include increased susceptibility to infection on a cellular level or decreased ability to clear infections. Papillomavirus (PV) infections are predominantly confined to keratinocytes, which are the only permissive cells in the epithelium. We are poised to determine whether male-derived keratinocytes and/or tissues have increased inherent susceptibility to PV infections and, in the process, we expect to identify cell factors that are differentially regulated in keratinocytes making them more susceptible to infection versus keratinocytes more resistant to infection. During the initial stages of an HPV or animal PV infection, the host keratinocytes possess a number of intrinsic (restriction) factors that can inhibit the establishment of infection. Additionally, innate immune signaling in keratinocytes determines whether innate effector cells are recruited and whether an effective adaptive immune response ensues. These keratinocyte-specific activities are likely to have a role in determining whether a PV infection will become persistent or will be cleared. Persistent HPV infections are more likely to progress to cancers. Clinical and epidemiological studies indicate a role for sex hormones in HPV pathology of the female genital tract; however, it is unclear whether the influence of sex hormones is due to increased HPV infection, increased viral persistence, or differential immunological regulation. In this application, we focus on the role of the host keratinocyte in the initial control of PV infection. Our decades of ground-work in studying molecular mechanisms controlling PV infections will permit us to determine whether/how sex-based differences impact the keratinocyte response to PV infection. In Aim 1 we will use a novel PV infection assay to quantitatively determine the susceptibility of human oral keratinocytes from male and female donors to HPV16 infection. In Aim 2 we will assess the susceptibility of male and female BALB/c FoxN1nu/nu mice to MmuPV1 infection and tumor formation. Five males and five females will be used to determine if the sexes differ in onset and extent of tumor formation. For each aim, we will assay infections and viral gene expression levels and correlate these with the expression of viral restriction factors and immune modulators in infected cells. We expect this pilot work to yield data foundational for a follow-up studies aimed to define more mechanistically the explanations for sex-based disparities in oncogenic HPV infections of the oral cavity.